Battery management system

ABSTRACT

The present invention relates to a battery management system for securely maintaining battery charging capacity and precisely measuring a battery pack voltage. The battery management system, which is coupled to a battery including a plurality of battery cells as one battery pack, includes a sensing stabilization unit, a relay, a battery pack voltage measurement signal generating unit, and an analog/digital (A/D) converter. The sensing stabilization unit includes a first and a second signal lines electrically coupled to a first and a second terminals of the battery, respectively, and maintains a stable potential difference between the first and second signal lines. The relay is turned on in response to a control signal, and transmits the potential difference between the first and second signal lines. The battery pack voltage measurement signal generating unit outputs a predetermined level of battery pack voltage measurement signal that is produced based on the potential difference between the first and second signal lines. The A/D converter receives the battery pack voltage measurement signal and converts it into a digital signal.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, andclaims all benefits accruing under 35 U.S.C.§ 119 from an applicationearlier filed in the Korean Intellectual Property Office on 20 Oct. 2005and there duly assigned Serial No. 10-2005-0099086.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery management system. Moreparticularly, the present invention relates to a battery managementsystem that can be used in a vehicle that is driven by electricalenergy.

2. Description of the Related Art

Vehicles using an internal combustion engine of gasoline or heavy oilhave caused serious air pollution. Accordingly, various efforts fordeveloping electric or hybrid vehicles have recently been made to reduceair pollution.

An electric vehicle uses an electric motor that is operated byelectrical energy outputted from a battery. Since the electric vehiclemainly uses a battery formed by one battery pack including a pluralityof rechargeable/dischargeable secondary cells, the vehicle hasadvantages that it has no emission gas and less noise than the vehiclethat uses combustion engine.

In the other hand, a hybrid vehicle commonly refers to agasoline-electric hybrid vehicle that uses an internal-combustion engineand an electric motor to drive the vehicle. Recently, hybrid vehiclesusing an internal-combustion engine and fuel cells and hybrid vehiclesusing a battery and fuel cells have been developed. The fuel cellsdirectly obtain electrical energy by generating a chemical reaction ofhydrogen and oxygen that are continuously provided to the fuel cells.

In these electric vehicle and hybrid vehicle, performance of a batterydirectly affects the performance of the vehicle that uses electricalenergy, and therefore each cell of the battery is required to have greatperformance. Also, a battery management system is required to measure avoltage and a current of the battery, and to efficiently managecharging/discharging operations of each battery cell.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present invention provides a battery management system for securelymaintaining battery charging capacity. In addition, the presentinvention provides a battery management system for precisely measuring abattery pack voltage.

An exemplary battery management system constructed as an embodiment ofthe present invention is coupled to a battery including a plurality ofbattery cells as one battery pack. An exemplary battery managementsystem includes a sensing stabilization unit, a battery pack voltagemeasurement signal generating unit, and an analog/digital (A/D)converter. The sensing stabilization unit includes a first signal lineand a second signal line electrically coupled to a first terminal and asecond terminal of the battery, respectively, and maintains a stablepotential difference between the first signal line and the second signalline. The battery pack voltage measurement signal generating unitoutputs a predetermined level of battery pack voltage measurement signalthat is produced based on the potential difference between the firstsignal line and the second signal line. The A/D converter receives thebattery pack voltage measurement signal and converts it into a digitalsignal.

The battery management system may further include a current controllingunit coupled to the first signal line and the second signal line of thesensing stabilization unit. The current controlling unit controlsamounts of the currents respectively applied to the first signal lineand the second signal line from the first terminal and the secondterminal of the battery. The current controlling unit may include afirst resistor coupled to the first signal line in series and a secondresistor coupled to the second signal line in series.

The battery management system may further include a noise eliminatingunit for eliminating a noise in the battery pack voltage measurementsignal outputted from the battery pack voltage measurement signalgenerating unit.

An exemplary battery management system constructed as another embodimentof the present invention includes a control signal generator, a cellvoltage measuring unit, a battery pack voltage measuring unit, a batterypack current measuring unit, and an analog/digital (A/D) converter. Thecell voltage measuring unit measures cell voltages of the plurality ofbattery cells, and outputs a plurality of cell voltage measurementsignals. The battery pack voltage measuring unit can be turned on whenThe battery pack voltage measuring unit receives an on-level of thecontrol signal from the control signal generator. The battery packvoltage measuring unit measures a battery pack voltage of the batterypack, and outputs a battery pack voltage measurement signal. The batterypack current measuring unit measures a battery pack current of thebattery pack, and outputs a battery pack current measurement signal. TheA/D converter receives the cell voltage measurement signals, the batterypack voltage measurement signal, and the battery pack currentmeasurement signal, and converts the signals to digital signals.

The battery pack voltage measuring unit may include a relay and abattery pack voltage measurement signal generating unit. The relay isturned on when the relay receives the on-level control signal, andtransmits a potential difference between a first output terminal and asecond output terminal of the battery. The battery pack voltagemeasurement signal generating unit generates a battery pack voltagemeasurement signal based on the potential difference transmitted by therelay.

The battery pack voltage measuring unit may include a first resistorcoupled to the first output terminal of the battery and coupled to afirst input terminal of the relay, and a second resistor coupled to thesecond output terminal of the battery and coupled to a second inputterminal of the relay. The battery pack voltage measurement signalgenerating unit may include an inverting differential amplifier forgenerating the battery pack voltage measurement signal.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or similar components, wherein:

FIG. 1 shows a diagram representing a battery, a battery managementsystem (BMS), and peripheral devices of the BMS that can be used in avehicle.

FIG. 2 shows a diagram of a configuration of a sensing unit constructedas a first exemplary embodiment of the present invention.

FIG. 3 shows a diagram of a configuration of a battery pack voltagemeasuring unit of the first exemplary embodiment of the presentinvention.

FIG. 4 shows a diagram of a configuration of a sensing unit constructedas a second exemplary embodiment of the present invention.

FIG. 5 shows a diagram of a configuration of a battery pack voltagemeasuring unit of the second exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, only certain exemplaryembodiments of the present invention have been shown and described,simply by way of illustration. As those skilled in the art wouldrealize, the described embodiments may be modified in various differentways, all without departing from the spirit or scope of the presentinvention. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. Like reference numeralsdesignate like elements throughout the specification.

Throughout this specification and the claims which follow, when it isdescribed that an element is coupled to another element, the element maybe directly coupled to the other element or electrically coupled to theother element through a third element. In addition, throughout thisspecification and the claims which follow, unless explicitly describedto the contrary, the word “comprise/include” or variations such as“comprises/includes” or “comprising/including” will be understood toimply the inclusion of stated elements but not the exclusion of anyother elements.

FIG. 1 shows a diagram representing a battery, a battery managementsystem (BMS), and peripheral devices of the BMS that can be used in avehicle. BMS 1, battery 2, current sensor 3, cooling fan 4, fuse 5, andmain switch 6 are shown in FIG. 1. Current sensor 3 measures an amountof an output current of battery 2, and outputs the measured amount ofoutput current to BMS 1. Cooling fan 4, in response to a control signalfrom BMS 1, reduces heat generated during charging/discharging processof battery 2, and prevents deterioration and reduction ofcharge/discharge efficiency of battery 2, which can be caused by atemperature increase of battery 2. Fuse 5 prevents an over-current,which may be caused by a disconnection or a short circuit of battery 2,from being transmitted to a power generator (not shown) of a vehicle.That is, when there is current overload, fuse 5 is disconnected so as toblock the over-current. Main switch 6 turns on or off battery 2 inresponse to a control signal sent from BMS 1 or a control signal sentfrom an engine control unit (ECU, not shown) when unusual phenomenon,such as an over-voltage, an over-current, and a high temperature,occurs.

Battery 2 includes eight sub-packs 210 to 280 coupled in series to eachother, positive output terminal 291, negative output terminal 292, andsafety switch 293 provided between sub-pack 240 and sub-pack 250.Sub-pack 210 includes five secondary battery cells coupled in series.Sub-packs 220 to 280 respectively include five secondary battery cells,and therefore battery 2 includes forty secondary battery cells.

Even though it is described, for better understanding in a firstexemplary embodiment of the present invention, that each sub-pack isformed by grouping five secondary battery cells as one group, battery 2may include the forty secondary battery cells directly coupled to eachother without being grouped into sub-packs 210 to 280.

Output terminals 291 and 292 are coupled to a power generator (notshown) of a vehicle to supply electrical energy to a vehicle engine. Thepower generator of the exemplary embodiment of the present invention iscan be an alternator. The alternator may be able to simultaneouslyfunction as a motor and a generator. The vehicle engine of the exemplaryembodiment of the present invention can be any type of engine capable ofdriving a vehicle such as a combustion engine, an electric motor, orcombinations thereof. Safety switch 293 is provided between sub-pack 240and sub-pack 250 to manually turn on or off battery 2 for the safety ofan operator when the operator handles or replaces battery 2. In thisexemplary embodiment of the present invention, safety switch 293 islocated between sub-pack 240 and sub-pack 250, but the location ofsafety switch 293 is not limited to this position, and can be changeddepending on the design of the system.

BMS 1 includes sensing unit 10, main control unit (MCU) 20, internalpower supplier 30, cell balance unit 40, storage unit 50, communicationunit 60, protection circuit unit 70, power-on reset unit 80, andexternal interface 90.

Sensing unit 10 measures an entire battery pack current, an entirebattery pack voltage, voltage of each battery cell, temperature of eachbattery cell, and peripheral temperature. Sensing unit 10 converts themeasured values into digital data, and transmits the digital data to MCU20. MCU 20 determines a state of charge (SOC) and a state of health(SOH) of battery 2 based on the digital data transmitted from sensingunit 10, and controls charging/discharging operation of battery 2.

Internal power supplier 30 supplies power to BMS 1 by using a backupbattery. Cell balance unit 40 balances the state of charge of each cell.That is, cells sufficiently charged are discharged, and cells relativelyless charged are further charged. Storage unit 50 stores data of thecurrent SOC and SOH when the power source of BMS 1 is turned off. Anelectrically erasable programmable read-only memory (EEPROM) may be usedfor storage unit 50. Communication unit 60 communicates with acontroller (not shown) of the power generator of the vehicle. Protectioncircuit unit 70 uses a firmware to protect battery 2 from shocks,over-currents, or low voltage. Power-on reset unit 80 resets the entiresystem when the power source of BMS 1 is turned on. External interface90 makes auxiliary devices of BMS 1, such as cooling fan 4 and mainswitch 6, be coupled to MCU 20. In this exemplary embodiment of thepresent invention, cooling fan 4 and main switch 6 are described asauxiliary devices of BMS 1, but the auxiliary devices can include othertypes of devices, and any number of auxiliary devices can be included.

FIG. 2 shows a diagram of a configuration of sensing unit 10 built as afirst exemplary embodiment of the present invention. As shown in FIG. 2,sensing unit 10 includes control signal generator 110, cell voltagemeasuring unit 120, battery pack voltage measuring unit 130, batterypack current measuring unit 140, temperature measuring unit 150, andanalogue/digital (A/D) converter 160.

Control signal generator 110 generates a control signal and outputs thecontrol signal to cell voltage measuring unit 120 in order to make cellvoltage measuring unit 120 sequentially measure voltages of the fortybattery cells. Cell voltage measuring unit 120 measures analogue cellvoltages of the forty battery cells of battery 2, and outputs themeasured voltages to A/D converter 160. Battery pack voltage measuringunit 130 measures an analog voltage between output terminals 291 and292, shown in FIG. 1, of battery 2, and outputs the voltage to A/Dconverter 160. Battery pack current measuring unit 140 receives thecurrent value measured by current sensor 3, shown in FIG. 1, andconverts the current value into an analog voltage signal. Battery packcurrent measuring unit 140 outputs the converted voltage signal to A/Dconverter 160.

A/D converter 160 converts the analog values received from cell voltagemeasuring unit 120, battery pack voltage measuring unit 130, and batterypack current measuring unit 140 into digital data, and outputs the datato MCU 20 shown in FIG. 1. In further detail, A/D converter 160 includesten input terminals, and sequentially converts the analog data receivedthrough the input terminals into digital data. Eight input terminals(referred to as the first to eighth input terminals) among the ten inputterminals are coupled to an output terminal of cell voltage measuringunit 120, another input terminal (referred to as the ninth inputterminal) is coupled to battery pack voltage measuring unit 130, and theother input terminal (referred to as the tenth input terminal) iscoupled to battery pack current measuring unit 140.

Temperature measuring unit 150 measures temperature inside battery 2 andperipheral temperature of battery 2, and outputs the measured values toMCU 20 as digital signals.

FIG. 3 shows a diagram of a configuration of battery pack voltagemeasuring unit 130 constructed as the first exemplary embodiment of thepresent invention. As shown in FIG. 3, battery pack voltage measuringunit 130 includes sensing stabilization unit 131, current controllingunit 132, attenuation unit 133, and noise eliminating unit 134.

Sensing stabilization unit 131 includes resistor 131 a and capacitor 131b. Resistor 131 a and capacitor 131 b are coupled in parallel betweensignal line 131+ coupled to positive output terminal 291 of battery 2and signal line 132− coupled to negative output terminal 292 of battery2. Resistor 131 a and capacitor 131 b cooperate to maintain a stablepotential difference between the signal line 131+ and the signal line131−. For example, if potential difference between signal line 131+ andsignal line 131− fluctuates due to a noise inputted to signal line 131+or signal line 131−, resistor 131 a and capacitor 131 b may filter thenoise and have the potential difference between signal line 131+ and thesignal line 131− maintained without noise. In this case, the capacitor131 b also maintains a voltage difference between both terminalsthereof. In other words, a voltage at the output terminal 291 and avoltage at the output terminal 292 are respectively applied to each ofthe terminals of the capacitor 131 b. In this case, when noises occur inthe voltages of the output terminals 291 and 292, the noises are alsotransmitted to the terminals of the capacitor 131 b, and voltages at theterminals of the capacitor 131 b are affected by the noises. However,since the noises at both of the terminals of the capacitor 131 b areoffset to each other, the voltage difference between both the terminalsof the capacitor 131 b may be maintained without noise. In addition, theresistor 131 a prevents inrush currents, and the sensing stabilizationunit 131 may not include the resistor 131 a.

Current controlling unit 132 controls the amounts of the currentsapplied to signal line 131+ and signal line 131− from positive outputterminal 291 and negative output terminal 292 of battery 2,respectively. Current controlling unit 132 includes resistor 132acoupled to signal line 131+ in series, and resistor 132 b coupled tosignal line 131− in series. Amounts of currents flowing through currentcontrolling unit 132 change due to resistors 132 a and 132 b. Forexample, when the battery pack voltage of battery 2 is 200 V, thecurrent is 0.1 mA when resistance of each of resistors 132 a and 132 bis 2 mega-ohm (MΩ). In this exemplary embodiment of the presentinvention, each of resistors 132 a and 132 b includes only one resistorof 2 mega-ohm, but can include two resistors coupled in series, each ofwhich has resistance of 1 mega-ohm.

Attenuation unit 133 is a battery pack voltage measurement signalgenerating unit for generating a signal corresponding to the batterypack voltage of battery 2. Attenuation unit 133 includes resistor 133 acoupled to a ground electrode, capacitor 133 b coupled to a groundelectrode, differential amplifier 133 c, and output terminal 133 d. Indifferential amplifier 133 c, which is an inverting differentialamplifier, a ground potential is inputted to a positive (+) inputterminal through resistor 133 a and capacitor 133 b, and a potential atpositive output terminal 291 of battery 2 is inputted to a negative (−)input terminal through resistor 132 a of current controlling unit 132. Abattery pack voltage measurement signal is outputted to output terminal133 d based on a potential difference between the ground potential andthe potential at positive output terminal 291. In the attenuation unit133, the magnitude of the battery pack voltage of battery 2, which isinputted through signal line 131+, is converted to the battery packvoltage measurement signal that has a scale between 0 V and 5 V.

Noise eliminating unit 134 eliminates the noise from a signal outputtedfrom output terminal 133 d of attenuation unit 133. A low pass filtermay be used for noise eliminating unit 134. An analog battery packvoltage measurement signal outputted from noise eliminating unit 134 isinputted to ninth input terminal of A/D converter 160, and is convertedinto a digital signal.

A second exemplary embodiment of the present invention will now bedescribed with reference to FIG. 4 and FIG. 5. FIG. 4 shows a diagram ofa configuration of sensing unit 10′ constructed as the second exemplaryembodiment of the present invention, and FIG. 5 shows a diagram of aconfiguration of battery pack voltage measuring unit 330 constructedaccording to the principles of the second exemplary embodiment of thepresent invention.

Differences from the first exemplary embodiment of the present inventionis that battery pack voltage measuring unit 330 of the second exemplaryembodiment of the present invention operates in response to a controlsignal transmitted from control signal generator 310. Because of suchdifference, the battery pack voltage can be more accurately measured,and a leak current can be effectively blocked when the power source ofBMS 1 is in off-state.

Since operations of cell voltage measuring unit 120, battery packcurrent measuring unit 140, temperature measuring unit 150, and A/Dconverter 160 are the same as those of the first exemplary embodiment ofthe present invention, detailed descriptions thereof will be skipped,and reference numbers thereof will be the same.

As shown in FIG. 4 and FIG. 5, control signal generator 310 generates acontrol signal, TOTAL_VOL_SW, and outputs the control signal,TOTAL_VOL_SW, to battery pack voltage measuring unit 330. Even though itis described that the control signal, TOTAL_VOL_SW, is generated incontrol signal generator 310 in this exemplary embodiment of the presentinvention, the control signal, TOTAL_VOL_SW, can be directly generatedin MCU 20 shown in FIG. 1 and be transmitted to battery pack voltagemeasuring unit 330.

Battery pack voltage measuring unit 330 measures the battery packvoltage of output terminals 291 and 292 of battery 2, based on thecontrol signal, TOTAL_VOL_SW. In further detail, referring to FIG. 5,battery pack voltage measuring unit 330 includes sensing stabilizationunit 131, attenuation unit 133, and noise eliminating unit 134, asincluded in battery pack voltage measuring unit 130 of the firstexemplary embodiment. Battery pack voltage measuring unit 330 furtherincludes current controlling unit 332 and a leakage prevention relay335.

Current controlling unit 332 includes resistor 332 a coupled to signalline 131+ in series and resistor 332 b coupled to signal line 131− inseries. Resistances of resistor 332 a and resistor 332 b may be smallerthan the resistance of resistor 132 a and the resistor 132 b shown inFIG. 3 of the first exemplary embodiment of the present invention. Forexample, when the battery pack voltage of the battery 2 is 200 V, thecurrent may be set to 1 mA by using resistors 332 a and 332 b of 200kilo-ohm (kΩ). While it has been described that each of resistor 332 aand resistor 332 b uses one 200 kilo-ohm (kΩ) resistor in the exemplaryembodiment of the present invention, they can be replaced with tworesistors of 100 kilo-ohm (kΩ) that are coupled in series.

Since the resistances of resistor 332 a and resistor 332 b are smallerthan the resistances of resistor 132 a and resistor 132 b of the firstexemplary embodiment of the present invention, the amounts of thecurrents outputted from current controlling unit 332 are increased.Accordingly, accuracy of the measurement of the battery pack voltage canbe improved, because attenuation unit 133 and noise eliminating unit 134more sensitively respond to slight variations of the currents. In theother hand, as the amounts of the currents outputted from currentcontrolling unit 332 are increased, the amounts of leakage currentsmaybe increased, which is the current generated while the power sourceof BMS 1 is off. However, the leakage currents may be efficientlyblocked by leakage prevention relay 335, which will now be described.

Leakage prevention relay 335 is turned on in response to the controlsignal, TOTAL_VOL_SW, outputted from control signal generator 310, andis turned off when BMS 1 is turned off. Leakage prevention relay 335connects signal line 131+ and signal line 131− to a negative (−) inputterminal and a positive (+) input terminal of differential amplifier 133c, respectively, when leakage prevention relay 335 is turned on. Butthere is no electrical connection between signal line 131+ and thenegative (−) input terminal, and between signal line 131− and thepositive (+) input terminal of differential amplifier 133 c, whenleakage prevention relay 335 is turned off.

The control signal, TOTAL_VOL_SW, has an on-level voltage when BMS 1 isturned on. That is, when the power source of BMS 1 is turned on, leakageprevention relay 335 is turned on. The control signal, TOTAL_VOL_SW, isalso referred to an on-level control signal. Since leakage preventionrelay 335 is turned off when BMS 1 is turned off, a leakage path ofcurrents generated by battery 2 to attenuation unit 133 (or a batterypack voltage measurement signal generating unit) is blocked.Accordingly, the leakage of currents from battery 2 can be completelyprevented, and therefore charging capacity of battery 2 can be securelymaintained.

According to the second exemplary embodiment of the present invention,since the leakage prevention relay is provided to the battery packvoltage measuring unit, the leakage currents generated by the batteryare blocked when the power source of the BMS is turned off, and thecharging capacity of the battery can be efficiently maintained. Becauseleakage current can be blocked by the leakage prevention relay 335, theamounts of the currents passing current control unit 332 can beincreased by the use of resistors having low resistance, and thereforethe accuracy for measuring the battery pack voltage can be improved.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A battery management system coupled to a battery, comprising: asensing stabilization unit including a first signal line and a secondsignal line coupled to a first terminal and a second terminal of thebattery, respectively, the sensing stabilization unit maintaining astable potential difference between the first signal line and the secondsignal line, the sensing stabilization unit further including a resistorand a capacitor that are directly connected in parallel at the same nodebetween the first signal line and the second signal line; a battery packvoltage measurement signal generating unit coupled to the sensingstabilization unit, and outputting a battery pack voltage measurementsignal that is produced based on the potential difference between thefirst signal line and the second signal line; and an analog/digital(A/D) converter coupled to the battery pack voltage measurement signalgenerating unit, and receiving the battery pack voltage measurementsignal and converting the battery pack voltage measurement signal into adigital signal.
 2. The battery management system of claim 1, furthercomprising a current controlling unit coupled to the first signal lineand the second signal line of the sensing stabilization unit, andcoupled to the battery pack voltage measurement signal generating unit,the current controlling unit controlling amounts of currents flowing tothe battery pack voltage measurement signal generating unit.
 3. Thebattery management system of claim 2, comprised of the currentcontrolling unit including: a first resistor coupled to the first signalline; and a second resistor coupled to the second signal line.
 4. Thebattery management system of claim 1, further comprising a noiseeliminating unit coupled to the battery pack voltage measurement signalgenerating unit, and eliminating a noise in the battery pack voltagemeasurement signal of the battery pack voltage measurement signalgenerating unit.
 5. The battery management system of claim 1, comprisedof the battery including a plurality of battery cells.
 6. A batterymanagement system coupled to a battery including a plurality of batterycells in a battery pack, comprising: a control signal generator forgenerating a control signal, the control signal generator generating anon-level control signal when the battery management system is turned on;a cell voltage measuring unit coupled to the battery, and measuringvoltages of the plurality of the battery cells and outputting aplurality of cell voltage measurement signals; a battery pack voltagemeasuring unit coupled to the battery and coupled to the control signalgenerator, the battery pack voltage measuring unit receiving the controlsignal from the control signal generator and measuring a battery packvoltage of the battery, the battery pack voltage measuring unitoutputting a battery pack voltage measurement signal, the battery packvoltage measuring unit including a sensing stabilization unit, thesensing stabilization unit including a resistor and a capacitor that aredirectly connected in parallel at the same node between a first signalline and a second signal line that are coupled to a first terminal and asecond terminal of the battery, respectively; a battery pack currentmeasuring unit coupled to the battery, and measuring a battery packcurrent of the battery and outputting a battery pack current measurementsignal; and an analog/digital converter receiving the cell voltagemeasurement signals, the battery pack voltage measurement signal, andthe battery pack current measurement signal, the analog/digitalconverter converting the cell voltage measurement signals, the batterypack voltage measurement signal, and the battery pack currentmeasurement signal to digital signals, respectively.
 7. The batterymanagement system of claim 6, comprised of the battery pack voltagemeasuring unit including: a relay being turned on when the relayreceives an on-level control signal from the control signal generator,the relay transmitting a potential difference between a first outputterminal and a second output terminal of the battery; and a battery packvoltage measurement signal generating unit coupled to the relay, andgenerating a battery pack voltage measurement signal produced based onthe potential difference transmitted by the relay.
 8. The batterymanagement system of claim 7, comprised of the battery pack voltagemeasuring unit including: a first resistor coupled to the first outputterminal of the battery and coupled to a first input terminal of therelay; and a second resistor coupled to the second output terminal ofthe battery and coupled to a second input terminal of the relay.
 9. Thebattery management system of claim 7, comprised of the battery packvoltage measurement signal generating unit including an invertingdifferential amplifier for generating the battery pack voltagemeasurement signal.
 10. The battery management system of claim 7,comprised of the relay not transmitting the potential difference betweena first output terminal and a second output terminal of the battery whenthe battery management system is turned off.